title: Cognitive processing speed has minimal influence on the construct validity of Multiple Sclerosis Walking Scale-12 scores.
abstract: BACKGROUND
  The Multiple Sclerosis Walking Scale-12 (MSWS-12) has been a commonly used patient reported outcome for measuring walking impairment in research involving multiple sclerosis (MS).
  
  
  OBJECTIVE
  We examined the possibility that cognitive processing speed (CPS) influences the association between MSWS-12 scores and other measures of ambulation (i.e., construct validity).
  
  
  METHODS
  96 MS patients completed the MSWS-12, underwent a neurological examination for generating an Expanded Disability Status Scale (EDSS) score, and completed the Symbol Digit Modalities Test (SDMT), Timed 25-Foot Walk (T25FW), 4 trials on the GAITRite™ for generating the functional ambulatory profile (FAP) score, and Six-minute Walk (6MW).
  
  
  RESULTS
  The SDMT was significantly correlated with MSWS-12 scores (r=-.428) and T25FW (r=-.459), 6MW (r=.512), FAP (r=.275), and EDSS (r=-.404) scores. There were statistically significant correlations between MSWS-12 and T25FW (r=.568), 6MW (r=-.680), FAP (r=-.595), and EDSS (r=.737) scores. Lastly, four separate hierarchical linear regression analyses indicated that, after controlling for age, gender, disease duration, and clinical course, T25FW, 6MW, FAP, and EDSS scores individually were significant correlates of MSWS-12 scores, and the associations (i.e., standardized beta-coefficients) were still statistically significant with minimal attenuation when controlling for SDMT scores.
  
  
  CONCLUSIONS
  There was minimal evidence that CPS influenced the construct validity of MSWS-12 scores.
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, United States. Electronic address: robmotl@illinois.edu.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Motl
authors.forename: Diego
authors.initials: D
authors.lastname: Cadavid
authors.forename: Brian M
authors.initials: BM
authors.lastname: Sandroff
authors.forename: Lara A
authors.initials: LA
authors.lastname: Pilutti
authors.forename: John H
authors.initials: JH
authors.lastname: Pula
authors.forename: Ralph H B
authors.initials: RH
authors.lastname: Benedict
mesh_terms: D000328:Adult; D000368:Aged; D003072:Cognition Disorders / Q000209:etiology*; D004185:Disability Evaluation; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D009103:Multiple Sclerosis / Q000150:complications*; D009483:Neuropsychological Tests; D012720:Severity of Illness Index; D013223:Statistics as Topic; D016138:Walking / Q000502:physiology*
keywords: Cognition; Gait; Measurement; Multiple sclerosis; Validity; Walking